This invention relates generally to record materials, and more specifically relates to record materials of the type having a sensitized surface which reacts to a colorless ink applied thereto by displaying distinctive colors in the image-configurated areas where said ink is present.
Within recent years a highly successful recording system has come into use based upon a multiple coloring principle in which an oily ink having two types of chromogenic reactants, normally colorless, is used upon an ink-receiving sheet sensitized with materials which react respectively with the two chromogenic substances to yield distinctive coloration. In one version of such system the said ink-receiving sheet is sensitized with substantially insoluble acid-like materials of high surface activity, such as attapulgite and zeolite, the chromogenic reactants being such substances as Crystal Violet Lactone and Benzoyl Leuco Methylene Blue. Such a system is disclosed, for example, in U.S. Pat. No. 2,712,507 to Barret K. Green, pertaining to the well-known "NCR" paper (the quoted phrase being a trademark of the National Cash Register Company), wherein the said ink is applied from an oversheet by pressure-release from microscopic capsules. In recording systems of this type the coloration of Crystal Violet Lactone is effected by an electron donor-acceptor solid-surface reaction with the acid clay-like mineral and the coloration of the Benzoyl Leuco Methylene Blue is brought about by hydrolysis followed by an oxidation-reduction reaction.
Because of the considerable time differential present with respect to completion of the two coloration reactions for the Crystal Violet Lactone and the Benzoyl Leuco Methylene Blue, an hiatus is often found to exist in the continuity of existence of the recorded marks produced by the previously described system. As such problem has been demonstrated to largely result from the fact that the two coloration reactions occur entirely via solid-surface reaction, improved record members have been developed wherein the coloration reactions are not dependent upon absorption on a solid surface-active material. Such an improved system is set forth, for example, in U.S. Pat. No. 3,455,721, wherein a record member is disclosed carrying in recording areas two types of microfine particles: the first an oil soluble acid-reactant organic polymeric material; the second, a colorless acid-type of mineral such as kaolin clay. When the previously described oily ink is applied to such a member, the polymeric particles enter the oil solution and promptly bring about the electron donor-acceptor reaction which effects coloration in Crystal Violet Lactone. At the same time contact of the oily ink with the acid type mineral initiates the oxidation reduction reaction which in time colorates the Benzoyl Leuco Methylene Blue dye. Because coloration of the Crystal Violet Lactone occurs in solution, the colored material is capable of entering the support sheet, and this coupled with the absence of particle contamination such as occurs where surface active particles are used, assures much greater persistence in coloration of the said dye.
Additional disclosures relative to the state of the art in which the present invention occurred may be found in U.S. Pat. Nos. 2,173,346; 2,463,501; 2,674,587; 3,516,845; 3,525,630; 3,535,412; British Pat. Nos. 1,212,731; 1,215,618; and Canadian Pat. Nos. 852,785 and 864,009.
The concept of using both an oil soluble polymer material and an acid-type mineral in the manner as set forth above, is less than satisfactory in the important respect that utilization of discrete particles of the one end of the other materials necessarily introduces undesirable discontinuitives into the recording surface, with a consequent loss of resolution and uniformity in the marking qualities of such surface. In particular it will be evident that even with the most uniform distribution of discrete particles, one particle type being uniformly dispensed among the other, coloration will occur--whether in the case of Crystal Violet Lactone or of Benzoyl Leuco Methylene Blue--at points spaced by the intervening alternate type particles. Such a result is compounded by the fact that ideal uniform distribution of one group of particle types among the other is, of course, not achieved in practice.